As he walked up a staircase in Orchard Road, he saw the man in front of him use a handphone to film under a woman's skirt.

IT specialist John Shen, 32, confronted the man, demanding that he stop what he was doing and surrender to the police.

Desperate to escape, the man, Teh Thian Seng, apparently took out several thousand dollars and offered it to Mr Shen in exchange for letting him go.

But in his mind, there was no question as to what he should do - reject the cash and hand Teh over to the authorities.

On Aug 25, 2012, Mr Shen was at the underground passageway between Ngee Ann City and Wisma Atriawhen he noticed Teh, who is married with two sons aged 17 and 20, behaving oddly.

Teh, 51, had switched on the video recorder function on his iPhone as he climbed a flight of stairs, following a woman closely.

Mr Shen told The New Paper on Thursday: "I remember thinking: 'This is a staircase, there's nothing to film. It's not like he's at a concert'."

He saw Teh position the iPhone underneath the woman's skirt with the camera facing upwards.

Mr Shen immediately confronted Teh.

He asked: "Excuse me, what are you doing?"

Teh replied: "Nothing."

Mr Shen refused to be intimidated and said firmly: "I saw what you were doing. You can't run. There are closed circuit television (cameras) everywhere. Stay put and let me call the security.

"You can either be frank with me or you can be frank with the police."

Teh meekly followed Mr Shen, who did not want to embarrass Teh in a crowded area.

CHANCE

Along the way, he begged Mr Shen to let him off, claiming it was his first offence and that he deserved a chance.

When that didn't work, Teh said he had a family he needed to support.

Mr Shen remained resolute. He told Teh: "Let the law decide. It's out of my hands now."

Desperate, Mr Shen claimed that Teh took out his wallet containing a thick wad of money, which Mr Shen estimated to be several thousand dollars.

He claimed that Teh whispered: "How much do you want for you to let me off?"

Mr Shen refused as he was afraid Teh would continue this pattern of behaviour. He told Teh that he was not tempted and that money would not solve anything.

Mr Shen recalled: "I approached Teh as a gentleman. I wanted to help rehabilitate him and to help him kick this bad habit.

"What if the victim's boyfriend was around and attacked him? Eventually, he would get caught and that person may not be as forgiving as I was."

Teh continued to plead and beg, saying: "This is not enough? How much do you want? Just tell me. I'll give."

But Mr Shen said he had already called the cops.

Teh then suggested that Mr Shen tell the police that he had escaped. He pleaded: "Give me a chance to delete the evidence."

"No," was Mr Shen's only retort.

WALK AWAY

The two men waited for the police for about 20 minutes. Mr Shen said that during that time, Teh tried repeatedly to walk away.

Mr Shen did not physically restrain Teh but merely reminded Teh that his face had already been captured on CCTV.

"If you run now, the punishment will only be more severe," Mr Shen cautioned Teh.

The police arrived, took statements from both parties and led Teh away.

Mr Shen told TNP that throughout the episode, he was not worried about Teh being violent. He added that as long as he remained cool and reacted in an appropriate manner, the matter could be resolved without escalation.

When told that Teh had been sentenced to three weeks in jail and fined $8,500, Mr Shen said: "I think the punishment fits the crime. He got what he deserved."

Quoting Dr Leong, Mr Joseph said: "The psychiatric conditions of paraphilia as well as clinical depression were contributing factors for him committing the offences."

However, Deputy Public Prosecutor Jeremy Lua pressed for a jail sentence. He stressed that paraphilia is not an impulse control disorder.

SEXUAL DEVIANCE

DPP Lua said: "His disorder relates to his preference, and the disorder of sexual paraphilia is largely a disorder of sexual preference... a form of sexual deviance. He can continue to seek help and treatment from the prison's medical services."

For each count of insulting a woman's modesty, he could have been jailed up to a year and fined.

And for having the obscene films, he could have been jailed up to six months and fined.